The invention relates to a measuring and evaluating device.
Such devices are used where the composition of gases has to be known for the control and/or regulation of a process. For determining the composition of gas, gas analyzers are used. The measured values determined by these devices are passed to an evaluating device separate from them. In the case of these devices, the accuracy of an analysis essentially depends on the use of suitable separating materials, detectors, the carrier gas and the operating conditions. The analysis time is essentially determined by the length of the separating column and the flow rate of the carrier gas/sample gas mixture through the separating column. The separating column used must in this case be all the longer the more similar the separating behavior of the components in the gas sample and the faster the travel rate of the gas sample through the separating column. For example, separating columns of 50 m in length are nowadays required for the separation of methane and ethane in the analysis of natural gas. For the analysis of high-boiling, long-chain hydrocarbons in the form of C5-C12, a length of 3 to 10 m is sufficient. Here it is also disadvantageous that with these devices the analysis times are very long. In the case of gas analyses for online process control, however, a short analysis time is very important. Furthermore, the application conditions in process gas analysis are such that the approximate composition of the medium to be investigated is known, and the intention is to determine the exact volume fraction of the main gas constituents. In the known process gas chromatographs, a short analysis time is achieved by using not just one separating column but generally at least two. In this case, a high-speed preliminary separation of the gas sample is carried out in a first column, with the fractions of the gas sample that are not of interest being separated out. Then, only those constituents of which the fractions are to be exactly determined are passed into the separating column. The production of such process gas chromatographs is very complex and expensive. The separating columns, valves and detectors have to be made individually for each device and put together individually for the respective application. Further essential, high-cost components of such a process gas chromatograph are the column oven and the housing. The column oven is required to allow the separating column to be operated at an increased, constant temperature of, for example, 70xc2x0 C. An increased temperature speeds up the transport of low-volatility components in the sample. Also known are special methods in which the sample is vaporized abruptly. With flash vaporizing, the readily volatile constituents are quickly separated out. For this purpose, the temperature of the column oven must be changed from, for example, 40xc2x0 C. to 140xc2x0 C. within just a few seconds. Another likewise known type of application of the column oven is operation with a slow temperature ramp, for example in the range between 40xc2x0 C. and 150xc2x0 C.
It is accordingly an object of the invention to provide a measuring and evaluating device that overcomes the above-mentioned disadvantages of the prior art devices of this general type, which has small dimensions with which process gas analyses can be carried out simply and quickly and the measurement results can be evaluated and displayed immediately.
With the foregoing and other objects in view there is provided, in accordance with the invention, a measuring and evaluating device for performing an analysis of gases. The device contains a central unit, at least one gas analyzer removably connected to the central unit, at least one evaluating unit integrated in the central unit, and a display unit integrated in the central unit and connected to the evaluating unit.
The measuring and evaluating device according to the invention is equipped with the gas analyzer configured as a module. This is releasably connected to the central unit of the measuring and evaluating device. The length and height of the central unit are less than 25 cm. Its width is less than 10 cm. The size of the gas analyzer is matched to these dimensions. Consequently, the measuring and evaluating unit can be easily transported and used at different locations. The central unit is provided, inter alia, with an evaluating unit, a display device and a power supply unit. Integrated in the gas analyzer are the components required for investigating a gas, such as a sample injector, a separating channel and detectors in the configuration required for taking samples, forward flushing, back flushing and also heart-cut or flip-flop operation.
In accordance with an added feature of the invention, the gas analyzer is a module and is connected directly to the central unit from the outside and is also connected to the evaluating unit. A power supply unit for supplying electrical power is integrated in the central unit. The central unit has supply lines ending in a plug-in connection for transporting a carrier gas, a gas to be analyzed and a calibrating gas, respectively.
In accordance with an additional feature of the invention, the gas analyzer has at least one plate and at least one separating channel integrated in the plate and the separating channel is releasably fitted in the gas analyzer.
In accordance with another feature of the invention, the plate has recesses formed therein functioning as the separating channel. A cover closes off the separating channel, and a separating material is applied to inside surfaces of the recesses and to inside surface of the covering facing the recesses, at least in a region of the separating channel.
In accordance with a further feature of the invention, the separating channel has a U-shaped cross section, and the plate and the covering are formed from a material selected from the group consisting of silicon, glass, metal and plastic. In addition, the separating material is hexamethyl disiloxane.
In accordance with a further added feature of the invention, the gas analyzer has at least one sample injector connected to the separating channel, and at least one detector is connected downstream of the separating channel.
In accordance with a further additional feature of the invention, the gas analyzer has a further detector connected upstream of the separating channel.
In accordance with another added feature of the invention, the separating channel is one of at least two separating channels provided in the gas analyzer. The sample injector is connected from the evaluating unit to at least one of the separating channels, and the separating channels are connected to the detector.
In accordance with another additional feature of the invention, the gas analyzer has at least one line for connecting the sample injector, the separating channel, and the detector to one another.
In accordance with an embodiment of the invention, the sample injector has at least three supply lines for transporting the carrier gas, the gas to be investigated and the calibrating gas, and are connected to the plug-in connection of a respective one of the supply lines of the central unit.
In accordance with a further embodiment of the invention, at least one heating and cooling device is integrated into either the gas analyzer or the central unit. The heating and cooling device can be a Peltier element. In addition, the heating and cooling device can be formed of a resistance heater and a Peltier element.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a measuring and evaluating device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.